This should show the DNS servers being used by the computer's cache. If it's showing nothing or something that should not be there try the following:

ipconfig /flushdns

followed by a

ipconfig /registerdns

Flushdns clears the local DNS cache while registerdns will communicate with the DHCP as well as DNS servers to re-register them. If this doesn't take care of the problem, it could very likely rest in his modem or router if using Broadband.